Technical Abstract:
The effect of management on the microbial community structure and enzyme activities of three semiarid soils from Southern High Plains of Texas were investigated. The soils (sandy clay loam, fine sandy loam and loam) were under continuous cotton (Gossypium hirsutum L.) or in cotton -peanut (Arachis hypogaea L.), -sorghum (Sorghum bicolor L.) or -wheat (Triticum aestivum L.) rotations, and had different water management (irrigated or dryland) and tillage practices (conservation: minimum, reduced, no-tillage, or conventional). The activities of beta-glucosidase, beta-glucosaminidase, alkaline phosphatase, and arylsulfatase were significantly (P<0.05) increased in the three soils when cotton was rotated with sorghum or wheat in comparison to continuous cotton. This was also true under conservation practices when compared to the corresponding rotation under conventional tillage. Principal Component Analysis (PCA) demonstrated high variability in the FAME profiles of the fine sandy loam compared to the loam explained by PC1 which accounted for 20 percent of the variance while the variability between the sandy clay loam and loam was explained by PC2 (13 percent of variance). The levels of a15:0 (bacteria indicator) ranged from 1.61±0.25% in cotton-peanut/irrigated/no-till (fine sandy loam) to 3.86±0.48% in cotton-sorghum/dry-land/conservation tillage (sandy clay loam) and the levels of 18:3w6c (fungi indicator) ranged from non-detectable in most of the samples of the sandy clay loam to 4.03±0.21 percent in sorghum-cotton/irrigated/conventional tillage (loam). No significant differences were detected in FAME profiles due to management within same soil in this year. Enzyme activities demonstrated the benefits of conservation practices and crop rotations over conventional practices with continuous cotton for semiarid soils.